So I think I've figured out the cause of the Xorg failures: The Asus M4N SLI series of motherboards all come with the onboard 750a and 980a (both 8200 derivatives) installed on the motherboard, and accessible despite the lack of headers is actually usable. My understanding is that Asus intends for the part to either be used as a PhysX co-processor, for HybridPower, and as part of Hybrid SLI. However, I just realized that no mention of support of these cores are made in the NVidia drivers at all, hence my belief that it is unsupported completely under Linux, even on boards that do have the headers and allow the core to function as a tertiary video adapter.

So comes my question: How do I set up my XOrg to ignore these? Or is it possible to have support for these in future NVidia drivers? I'd be interested to see HybridPower implemented for these.

Hybrid power is abandoned. If you search the forums you will see that there is no plan to support them. That being said, I also have Asus boards with 750a and 780a chipsets and they do work under linux with current and past drivers.

Hmmm, odd. I was not able to get into X when the 750a is enabled. Keeps getting a "Failed to allocate 2D engine" and "Fail to allocate 2D object" error. Unless I force a reinstall of the NVidia drivers, which causes X to work until the next reboot, but while in X the 750a was not reported by nvidia-settings.

How do I force Xorg to not see the 750a without needing it disabled? Or is it caused by something else (i.e. AppArmor)?